Ultrafine palladium particles supported on chelate resin–metal complexes: promotion effect of lanthanide ions on catalytic activity

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Abstract
Dry beads of chelate resin–metal complexes have been prepared as catalysts from a resin based on polystyrene functionalized by tridentate iminodiacetate (ida) moieties by both complexing of metal ions and supporting of ultrafine palladium particles. Two methods were employed. When [PdCl4]2– ions were contacted with a chelate resin without metal ions (acid type) or with divalent metal ions, ultrafine palladium particles, produced by subsequent reduction, were distributed only on the surface of the resin. On the other hand, when [PdCl4]2– ions were contacted with a chelate resin having trivalent metal ions (which has anion-exchange ability), the palladium particles were distributed uniformly in the resin. The supported ultrafine palladium particles catalyse the hydrogenation of CC bonds, the activity greatly depending on both the metal ions co-ordinated to the ida moieties and the distribution of the palladium particles in the resin. While catalysts with palladium particles on the surface of the resin had higher catalytic activity than those with particles inside the resin, palladium particles supported on chelate resin-lanthanide complexes had higher activity than those supported on resin–divalent metal complexes in spite of the uniform distribution of the palladium particles in the resin in the case of the lanthanide complexes. The promotion effect of the co-ordinated lanthanide ions varied with the atomic number of the latter, catalysts with unstable numbers of 4f electrons showing the highest catalytic activity.